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Schematic diagram of 304 nm-band AlGaN-based UVB-LED. [24] Copyright 2022, Springer Nature Publishing.
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The current pandemic crisis caused by SARS-CoV-2 has also pushed researchers to work on LEDs, especially in the range of 220–240 nm, for the purpose of disinfecting the environment, but the efficiency of such deep UV-LEDs is highly demanding for mass adoption. Over the last two decades, several research groups have worked out that the optical power...
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... design provided a substantial improvement in the efficiency and light output power of about 8.2% and 36 mW respectively. Even in the absence of standard package, they observed an improved efficiency of up to 9.6% and Pout of 40 mW by the structure as shown in Figure 7. The different manufacturing techniques and their outcomes are compared in Table 1 ...
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Conventional deep-ultraviolet (UV) light-emitting diodes (LEDs) based on AlGaN crystals have extremely low light-emission efficiencies due to the absorption in p-type GaN anode contacts. UV-light-transparent anode structures are considered as one of the solutions to increase a light output power. To this end, the present study focuses on developing...
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... Over the past few years, AlGaN-based ultraviolet light-emitting diodes (LEDs) emitting between 260 nm and 280 nm (near-UVC) have the potential to supersede conventional mercury lamps in sterilization and disinfection fields, due to their various advantages of miniaturization, short switch times, low operation power, and environmental friendliness [1][2][3][4]. Especially, the worldwide spread of the SARS-CoV-2 virus has further raised demands for improving the performance and reliability of UVC LEDs to boost market penetration [5]. ...
Heteroepitaxial growth of high Al-content AlGaN often results in a high density of threading dislocations and surface hexagonal hillocks, which degrade the performance and reliability of AlGaN-based UVC light emitting diodes (LEDs). In this study, the degradation mechanism and impurity/defect behavior of UVC LEDs in relation to the hexagonal hillocks have been studied in detail. It was found that the early degradation of UVC LEDs is primarily caused by electron leakage. The prominent contribution of the hillock edges to the electron leakage is unambiguously evidenced by the transmission electron microscopy measurements, time-of-flight secondary ion mass spectrometry, and conductive atomic force microscopy. Dislocations bunching and segregation of impurities, including C, O, and Si, at the hillock edges are clearly observed, which facilitate the trap-assisted carrier tunneling in the multiple quantum wells and subsequent recombination in the p-AlGaN. This work sheds light on one possible degradation mechanism of AlGaN-based UVC LEDs.
This paper presents an extensive literature review on Light-Emitting Diode (LED) fundamentals and discusses the historical development of LEDs, focusing on the material selection, design employed, and modifications used in increasing the light output. It traces the evolutionary trajectory of the efficiency enhancement of ultraviolet (UV), blue, green, and red LEDs. It rigorously examines the diverse applications of LEDs, spanning from solid-state lighting to cutting-edge display technology, and their emerging role in microbial deactivation. A detailed overview of current trends and prospects in lighting and display technology is presented. Using the literature, this review offers valuable insights into the application of UV LEDs for microbial and potential viral disinfection. It conducts an in-depth exploration of the various microorganism responses to UV radiation based on the existing literature. Furthermore, the review investigates UV LED-based systems for water purification and surface disinfection. A prospective design for a solar-powered UV LED disinfection system is also delineated. The primary objective of this review article is to organize and synthesize pivotal information from the literature, offering a concise and focused overview of LED applications. From our review, we can conclude that the efficiency of LEDs has continuously increased since its invention and researchers are searching for methods to increase efficiency further. The demand for LED lighting and display applications is continuously increasing. Our analysis reveals an exciting horizon in microbial disinfection, where the integration of UV LED systems with cutting-edge technologies such as sensors, solar power, Internet-of-Things (IoT) devices, and artificial intelligence algorithms promises high levels of precision and efficacy in disinfection practices. This contribution sets the stage for future research endeavors in the domain of viral disinfection using solar-powered UV LED modules for universal applications.
This research is focused on the development of a UV-C LED lamp designed for effective water disinfection, tackling as a primary issue the low quantum efficiency and significant self-heating due to elevated operating currents which reduce the LED performance. By conducting thorough characterization and employing strategies including aluminum heat sinks and varied electrical biasing methods such as constant current, PWM, and high-current short-time pulses. The study assesses the disinfection potential against pathogenic bacteria such as Escherichia coli and Salmonella. Results indicate successful E. coli inactivation within agar mediums and notable growth suppression in Mueller-Hinton culture mediums, as confirmed through optical density measurements. Therefore, this investigation underlines the importance of optimized operational strategies to enhance UV-C LED lamps' disinfection capabilities.
The trap behavior and its effect on recombination in the degradation of AlGaN-based deep ultraviolet light-emitting diodes (LEDs) under constant current stress are investigated in this work. The Shockley Read Hall (SRH) recombination of vacancies plays a significant role in the degradation of the device, and the trap-assisted radiative recombination also has a certain contribution. The increase in vacancies comes from two mechanisms: 1) the degradation of the lattice under stress and 2) the release from the associated complex of vacancies that exist in the fresh device under stress. The impact of vacancies on device degradation also has two mechanisms: 1) act as a non-radiative recombination center and participate in SRH recombination and 2) form complexes with the acceptor impurities under stress and enhance trap-assisted radiative recombination. These failure mechanisms severely affected by current expansion in large-area devices. The increase of nitrogen/gallium vacancies and vacancies-magnesium complexes and the decrease in native vacancy complexes and interfacial states are speculated according to deep level transient spectrum and admittance spectroscopy. This study provides an in-depth analysis of the defect behavior and recombination induced by electrical stress in UV-C LEDs and suggests possible optimization directions for the fabrication of high-reliability AlGaN-based large-area devices.
